An oil filter is an essential component of a vehicle's lubrication system. Its purpose is to remove contaminants and impurities from the engine oil, ensuring that the oil stays clean and provides effective lubrication. Car oil filters consist of a cylindrical housing with a filter media inside, which captures dirt, metal particles, sludge, and other contaminants.

Types of oil filters

Spin-on filters: Spin-on filters are the most common type found in vehicles. They have a self-contained design with the filter media and housing combined into a single unit. They are easy to install and replace during routine oil changes. The entire filter is typically replaced as a unit.
Cartridge filters: Cartridge filters consist of a replaceable filter element housed in a separate housing. When it's time for an oil change, only the filter element is replaced while the housing is retained. Cartridge filters are more environmentally friendly since only the filter element needs to be disposed of.
Magnetic filters: Magnetic filters use a magnet or magnetic material to attract and capture metallic particles in the engine oil. These filters are particularly effective in trapping small metal shavings and debris. They are often used in conjunction with other types of filters to enhance filtration efficiency.

What happens if you change the oil filter but not the oil?

Changing the oil filter without changing the oil is not recommended. When you change the oil filter but not the oil:

Contaminants remain: By not changing the oil, contaminants like dirt, metal particles, sludge, and combustion by-products will continue to circulate, potentially causing increased wear and damage to the engine.
Reduced filtration efficiency: The new filter may quickly become overwhelmed by the remaining contaminants in the old oil, reducing its effectiveness and potentially allowing contaminants to bypass the filter and circulate in the engine.
Degraded oil properties: Retained oil may have lost its lubricating properties, viscosity, and thermal stability, leading to inadequate lubrication, increased friction, heat, and potential wear on engine components.
Missed maintenance opportunity: Not changing the oil means missing out on the opportunity to remove contaminants, refresh the lubrication system, and ensure optimal engine performance through a comprehensive oil change.

In short, changing only the oil filter without changing the oil can lead to retained contaminants, reduced filtration efficiency, potential engine damage, and missed maintenance benefits. It is best to perform complete oil changes for optimal engine health and performance.